How Holes Move

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Science  17 Oct 2008:
Vol. 322, Issue 5900, pp. 349
DOI: 10.1126/science.322.5900.349b

Quantum mechanics can explain how a single electron behaves in the presence of an oppositely charged proton. Add just one more electron, however, and the analysis becomes vastly more complicated. Because electrons affect one another, any motion by one of them must be considered in the context of correlated motion by the other—a scenario that proves ever more challenging to model as the number of electrons grows to molecular proportions. Lünnemann et al. explore the underlying effects of this correlated behavior in a computational study of how three molecules respond to ionization. After removing the most weakly bound electron from a phenyl, ethylene, or butadiene group tethered to an amine, the rate at which the resulting positive charge migrates to the nitrogen center was calculated. Because this delocalization is mediated by correlation effects rather than charge flow kinetics, the rates are extremely rapid (several femtoseconds). Migration is effectively total for the butadiene substrate, partial for the phenyl substrate, and minimal for the ethylene substrate. These trends are highly sensitive to molecular conformation and vary when the torsion angle of the amine is shifted. — JSY

J. Chem. Phys. 129, 104305 (2008).

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